Cishe wonke amapulasitiki athambekele ekuwohlokeni lapho evezwe ukukhanya kwe-ultraviolet, njengokukhanya kwelanga noma ukukhanya kwe-fluorescent. Lokhu konakala kungenzeka ngesikhathi sokucutshungulwa noma uma umkhiqizo ususetshenziswa, futhi izimpawu zawo zihlanganisa ukonakala, ukuguquguquka kombala kanye nokulahlekelwa izinto ezibonakalayo ezifana namandla okuthinta, amandla aqinile kanye nombala - konke okuholela ekunciphiseni ukuphila kwepulasitiki. Isibonelo sansuku zonke sokucekelwa phansi kwe-UV yisihlalo sotshani esingashintsha umbala futhi sibe brittle ngokuhamba kwesikhathi ngenxa yokuwohloka kwepulasitiki.
Izithasiselo zokuqiniswa kwe-UV ziyinhlanganisela engezwe ukuvimbela ukuwohloka kwepulasitiki futhi andise kakhulu impilo yomkhiqizo wokugcina. Iziqinisi ze-UV zengezwa emazingeni aphansi kakhulu, ngokuvamile angu-0.1 - 0.5% we-polymer. Lezi zithako ngokuvamile zingahlanganiswa ne-polymer eyisisekelo ngesikhathi sokukhiqiza noma zilungiswe njengengxenye ye-masterbatch. Kukhona izithasiselo eziningi emakethe zokuqiniswa kwe-UV okuhlanganisa i-Amshield, i-Amcor's Ultra Violet Inhibitor stabilizer.
Iyini i-Photooxidation?
Ukuwohloka kwepulasitiki okubangelwa ukukhanya kwe-UV kuwumphumela wenqubo yamakhemikhali ebizwa ngokuthi i-photooxidation noma i-photodegradation. Ukukhanya kwe-UV kwehlisa izibopho zamakhemikhali ezikhona emaketangeni e-polymer, kwenza ipulasitiki ibe buthaka ngokunciphisa isisindo sayo samangqamuzana, okuholela ekulahlekelweni kwamandla nezinye izimpawu ezingathandeki, njengoba kuchazwe ngaphambilini. Ukuwohloka kwamangqamuzana, njenge-photooxidation, ngokuvamile kubangela ukuba amapulasitiki ahluleke, ngakho-ke kubalulekile ukuqonda lezi zinqubo nokuthi ungazigwema kanjani!
Ukumelana kwe-UV kwama-polymers angavikelekile kuyahlukahluka, kuye ngesakhiwo nokwakheka. Amanye amapulasitiki angenwa kalula yi-photooxidation ngenxa yesakhiwo sawo namaqembu asebenzayo. Amabhondi angenwa kalula yi-photooxidation ahlanganisa i-carbon-amabhondi e-nitrogen afana nama-nitriles, ama-amide, nama-amine; amabhondi e-carbon-oxygen afana nama-ether, ama-ester, ama-ketone, nama-carboxylic acid; carbon-amabhondi e-chlorine; i-oxygen-amabhondi oksijini njengama-peroxides; kanye namabhondi e-nitrogen{6}i-hydrogen afana nama-amide nama-amine.
Izinhlobo ze-UV Stabilizing Additives
Ukuvimbela inqubo ye-photooxidative nokuvikela amapulasitiki emisebeni ye-UV eyingozi, kusetshenziswa iziqinisi ze-UV. Ukuvikelwa kwe-UV kunganikezwa ngezindlela ezihlukene kuye ngokuthi isizinzisi se-UV esisetshenzisiwe esisetshenzisiwe. Imvamisa, izinhlobo ezijwayeleke kakhulu zezithasiselo zisebenza njengezibambisi ze-UV, okokucima umlilo, noma i-HALS, futhi kwezinye izimo kungasetshenziswa izithasiselo ezingaphezu kwesisodwa ukuze kuhlinzekwe izinga elifiswayo lokuzinza kwe-UV.
Izithambisi ze-UV: Ekufakweni kokukhanya okwanele, amaqembu asebenzayo azwelayo (abizwa ngokuthi ama-chromophores) kuma-polymer abhekana nochungechunge lokusabela ukuze akhiqize ama-radicals mahhala. Leli fomu le-UV stabilizer, njengoba negama liphakamisa, lidonsa imisebe ye-UV ukuvimbela ukuqaliswa kokusabela kwe-photooxidative. Lapho ukushisa kwe-UV sekumuncwa, kuhlakazwa ngamaketanga e-polymer. Umnyama uyisimunyisi se-UV esihle kakhulu, ngakho-ke opende, odayi, noma i-elemental carbon black kuvame ukungezwa ukuze kuvikelwe imikhiqizo yepulasitiki emisebeni ye-UV. I-Benzotriazoles kanye ne-hydroxyphenyltriazines nazo ziyizibonelo zokumunca i-UV.
Izicisha: Inqubo-ye-oxidation yesithombe ibandakanya ukusabela okuningi ekugcineni okukhiqiza ama-radicals mahhala asabela ngamabhondi amaningi kuketango le-polymer, acekele phansi ubuqotho bepulasitiki. Izicishi zisebenza ngokucisha amandla akhiqizwa ngesikhathi sokusabela kwe-photooxidation, ngaleyo ndlela, zibuyisela ama-molecule ajabulile esimweni esiphansi lapho mancane amathuba okuthi asakaze i-free radical{2}}ekhiqiza ukusabela kwe-photooxidation. I-nickel quencher iyisibonelo salolu hlobo lwe-UV stabilizer.
I-HALS: I-Amine Light Stabilizer (i-HALS) Evinjelwe (i-HALS) iyizinzinzisi ze-UV ezikhomba futhi zicuphe ama-radicals mahhala akhiqizwa phakathi-ne-oxidation yesithombe, eziwavimbela ukuthi zisabele ngesakhiwo se-polymer. Isakhiwo se-HALS siyahlukahluka, kodwa ngokuvamile sinesakhiwo sendandatho ye-2,2,6,6-tetramethylpiperidine.
